The present invention relates to a regulated flow restrictor device. The invention is particularly useful for drip irrigation emitters, and is therefore described below with respect to this application, but it will be appreciated that the invention could be used in other applications, such as flow-regulators for water sprinklers, medical infusion sets, fluid heating and cooling systems, and the like.
Drip irrigation systems have come into widespread use for irrigating plants since they supply a minimum of water directly to the root region of the plants. Regulated emitters have also come into widespread use since they produce a fairly uniform output despite variations in the inlet pressure, and thereby enable drip irrigation lines to be of relatively long lengths and to be used over uneven terrain.
Many techniques have been developed for regulating emitters. Some involve varying the cross-section of a labyrinth in response to changes in the inlet pressure; whereas others involve varying the cross-section of a control chamber or of an outlet port in response to changes in the inlet pressure. Another proposed technique, as described in Eckstein U.S. Pat. No. 5,111,996, varies the effective length of a labyrinth in response to changes in the outlet pressure.
In addition, there are many applications in agriculture, medicine and other fields, wherein it is desirable to regulate the flow of a fluid so as to maintain a relatively constant rate despite variations in the fluid pressure, but also to permit the flow rate to be conveniently changed to a new rate and to be maintained at the new rate despite variations in the fluid pressure. For example, in the agricultural field it is frequently desirable to set a predetermined flow rate for an irrigation dripper or water sprinkler at an early stage of a crop to be irrigated, and to increase the flow rate at later stages; in the medical field, it is frequently desirable to change the flow rate of a medical infusion set according to the particular circumstances. However, in the known devices now in use, a change in the flow rate generally also significantly affects the regulating performance of the flow control device in the new flow rate.
My above-cited application Ser. No. 08/099,509 describes a regulated flow restrictor device particularly useful as a drip irrigation emitter, comprising a housing having an inlet opening connectible to a source of pressurized fluid, an outlet opening, and a passageway including first and second opposed walls connecting the inlet opening to the outlet opening. One of the walls is displaceable towards and away from the other wall. The device further includes a plurality of baffles extending transversely of, and longitudinally spaced between, the first and second walls to define a flow-restrictor imposing a resistance to the flow of the fluid through the passageway. The baffles define clearances with the passageway walls, which clearances, by the displacement of the displaceable wall, vary the resistance of the flow of the fluid through the passageway in response to variations in the pressure of the pressurized fluid.
An important feature in the device of that application is that the clearances are of increasing height in the direction from one of the openings towards the other of the openings such that the clearances are sequentially closed with increasing pressure of the pressurized fluid to maintain a substantially uniform flow to and through the housing outlet opening despite variations in the pressure of the pressurized fluid.
As described in that application, the clearances defined by the baffles are controlled in response to variations in the inlet pressure, to thereby provide continuous and substantially uniform regulation of the outlet flow in response to variations in the inlet pressure. Such a regulated flow restrictor device may be provided with relatively large passageways, thereby reducing the sensitivity of the device to clogging. Further, since all the baffles are subjected to the flow even when the inlet pressure is relatively low, as occurring at the start and finish of an irrigation operation, the novel construction is inherently capable of self-flushing itself during irrigation and particularly at the start and end of an irrigation operation.
In the examples of the devices described in that patent application, the clearances are of increasing height from the housing inlet towards the housing outlet.